Last time I checked the iPhone recorded GPS coordinates as part of the EXIF tag when you take a photo. All you'd have to do is take a shot yourself every half hour or so. You were planning on taking pictures anyway, right?
In any case - you'll need to be in an area that gets a signal from your provider to make anything like that work - which isn't always as seemless as they'd like to make it look on their coverage claims.
Last edited by Burton; 04-18-13 at 07:01 AM.